Biogenic amines and prostaglandins have been implicated as mediators and/or modulators of a variety of hormone effects in the genital tract. Nevertheless, the specific roles of these mediators remain to be elucidated because of: 1) previous technical limitations in the assay of the subnanogram levels of these potent substances 2) lack of histochemical methods suitable for their localization and 3) failure to consider that hormone responses might involve interaction of biogenic amines and prostaglandins, rather than independent action of one or the other of the mediators. The objectives of this study are to determine how biogenic amines and prostaglandins mediate and/or modulate hormone action in the genital tract. A multidisciplinary approach consisting of concurrent study of localization, biochemical mechanisms, and determinations of physiologic changes is to be used. Current emphasis is upon the correlation of uterine blood flow and contractility with the biogenic amines and prostaglandins in normal, cycling animals and in a biologic model system (castrate animals stimulated by known amounts of estrogen). The normal responses of these systems and the responses elicited after pharmacologic manipulation of the biogenic amines and prostaglandins are to be the basis of later studies of distortions of normal uterine function: toxemia of pregnancy and the intrauterine contraceptive device.